Caption: Scanning electron micrograph (SEM) of Freshwater cnidarian (Hydra sp.). Hydra is a small freshwater coelenterate in the family Hydridae. It has a stalk-like tubular body and a ring of tentacles around its mouth. Hydras belong to the phylum Coelenterata (also called Cnidaria), which includes corals, sea anemones and jellyfish. Coelenterates are primarily marine animals, but hydras are found in freshwater ponds, lakes, and streams. The tentacles possess nematocyts and when the prey gets close to the tentacle the nematocysts fire into the prey. The tentacle then coils around the prey to bring it to the mouth region. They are native to temperate and tropical regions. Scientists are interested in Hydra because of their regenerative ability. Magnification x14 when shortest axis printed at 25 millimetres.